The long term objective of this research is to incorporate methods of computational fluid mechanics into the industrial hygiene engineering field. The purpose is to improve the design of ventilation systems used to control worker exposure to toxic airborne contaminants. Ventilation remains one of the primary engineering controls selected to protect workers, yet design procedures rely on methods developed at the turn of the century. Computational methods are employed in virtually all engineering disciplines for design and prediction, yet are almost non-existent in contaminant-control ventilation applications. The specific aims of this proposal are: (1) to expand an existing computer code to predict air flow patterns around a worker and a nearby obstacle; (2) to develop models of exposure from these flow fields, and (3) to conduct flow visualization and tracer gas experiments with a mannequin in a wind tunnel to validate the computer predictions. Computer codes will be developed on personal computers but will need to run on larger machines to address the problems described above. Wind-tunnel experiments will employ sulfur hexafluoride as the tracer gas and use a real-time infrared spectrophotometer for concentration measurements. Flow visualization will be accomplished with a bubble generator and smoke wire technique. Video recordings of the flow patterns will be obtained.